When it comes to sandwiches, it turns out size really does matter.

Across the country, from east London to Edinburgh, supersized sarnies with a girth of at least four inches are trending. In the hours leading up to lunchtime you’ll find customers queueing around the block before that day’s batch of colossal carbs sell out. And while some outlets have a “stack it high and sell it cheap” approach, others are constructing towering sarnie structures using seasonal and organic produce with prices hovering around the £12 mark.

At the Dusty Knuckle in Dalston, east London, wedges of roasted beetroot are smothered in a harissa dressing, topped with a herby salad, sprinkled with almonds and shoved between two pillowy soft slabs of focaccia. At Mondo Sando in Camberwell, south London, its chewy white baguettes feature layers of salami, capicola squeezed between mozzarella and hot peppers, while one of the most popular sandwiches at Alby’s in Southside, Edinburgh, features chunks of battered chicken thighs covered in crispy onions and wedged between doorstep slices. Elsewhere, The Bear’s Matty Matheson’s forthcoming cookbook includes recipes for precipitous pork sandos and French dip rolls.

Edd Watkinson who runs the Big Deal’s Bodega in Norwich, which sells giant sarnies featuring everything from peaches to samosas, says the key to the gargantuan trend is “providing customers with a sandwich that’s so far removed from a sandwich they’d make themself at home”.

“The sandwich is on an upward trajectory,” says Max Halley, who 10 years ago quit his job as a chef in a Michelin-starred restaurant to open Max’s Sandwich Shop in north London. Current bestsellers on Halley’s menu include ham, egg ’n’ chips and goat tikka masala with a gravy mayonnaise. Halley says they are “a meal” rather than “a convenient snack”.

The food writer Jonathan Nunn, who runs the popular newsletter Vittles, attributes some of the super sarnie’s success to the UK’s fascination with Americana. “In the early 2010s this was about burgers and barbecue, but now it’s become about regionality, which is ideal for sandwiches,” Nunn says

Max Tobias, who co-founded the Dusty Knuckle with two friends in 2014, selling XXL sandwiches from a shipping container in a car park, credits a wider growing interest in local and seasonal ingredients alongside people spending more on little day to day treats rather than splurging on holidays as boosting the trend.

Tobias, who sells on average 350 sandwiches – starting price £10.95 – each Saturday, says their offerings riff on the idea of small plates restaurants. “The level of intricacy, care and detail of cooking and seasonal, fresh ingredients that go into these sandwiches is at least on a par with, if not outstripping, what you’re going to get in lots of very decent restaurants. If you deconstructed our sandwich and put it on a plate, you’d be paying twice the money for it in a fancy restaurant.”

This detailed approach is a far cry from the sandwich’s origins, which are credited to John Montagu, the fourth Earl of Sandwich. In 1762 during a game of cards at a private member’s club in London, Montagu is said to have ordered “a bit of beef between two slices of toasted bread” so that he could eat it with his hands and not leave the gaming table. By the mid-19th century, ham sandwich street vendors were popular in London and in 1980 M&S introduced packaged versions. Now with many workers taking a hybrid approach to the office, the sad supermarket sandwich, often seen as an emblem of busyness, is facing some sizeable competition.

“Our sandwiches are the opposite of grabbing something from a chain,” Tobias says. “They force you to sit down. It’s going to be messy. It’s going to be outrageously delicious. You have to stop what you are doing and appreciate it. It’s a moment.”

Nichola Ludlam-Raine, a dietician and author of How Not to Eat Ultra-Processed?, suggests eating half of a supersized sarnie and saving the other half for later. Tobias says many customers opt to share or consider it a treat.

Nunn also cautions against some interpretations. “All the great American sandwiches come from cities with an abundance of a certain ingredient, and a specific working-class diaspora, which led to the creation of large, filling sandwiches.” Nunn says that some are “importing the form without the culture and knowledge of how to make them, leading to oversized, overstuffed creations that disrespect the diameter of the human mouth.”

So how big is too big when it comes to actually attempting to eat a herculean-sized sandwich? Halley says you need to be able to “take a bite of it and get the filling and both the top and bottom bread.” He constructs his sandwiches with each component in a certain order so that it tastes best.

“Others construct them so that the order looks best on Instagram,” he adds. “For me they are two different things. One is concerned with deliciousness. The other is concerned with the aesthetic which is the perception of deliciousness. That isn’t real.”